.b{
    width: 100px ;
    height: 100px;
    margin: 10px;
    border: 2px solid #2e317c;
} 
.f{
    border: 2px solid #2e317c;
    width: 100px;
    margin: 10px;
}
.s{
    border: 2px solid #2e317c;
    width: 100px;
    height: 100px;
}
.s:nth-child(1){
    border: 2px solid #2e317c;
    margin-top: 10px;
}
.s:nth-child(2){
    border: 2px solid #2e317c;
    margin-bottom: 10px;
}